Project Summary The RNA Exosome and SKI complex are major cellular machines that degrade host RNA. This machine is required for several reasons in the cell including maintenance of current RNA levels and to reduce the level of cytoplasmic RNA such that the RIGI and MDA5 sensors can detect viral RNA other than host RNA. The SKI complex was identified in a genetic screen as a host protein that interacts with both Influenza NS1 and MERS-CoV ORF4a. We were able to demonstrate that knocking down these proteins in cells caused a reduction in viral replication and an increase in Interferon stimulated gene induction, irrespective of whether a virus was there or not. The SKI complex in yeast has been crystalized and upon modeling of the human structure, we in silico identified compounds that could potentially bind to a member of the complex, WDR61. In cell culture experiments, we identified 4 compounds from the 40 identified in the modeling, that block Influenza virus, MERS-CoV and SARS-CoV replication. In this proposal, we will determine the mechanism of action of the compounds and NS1 and ORF4a on the SKI complex. We will also initiate in vivo studies to evaluate the antiviral effectiveness of the SKI targeted plasmids on Influenza virus and MERS-CoV mouse models. This work will validate a novel host target and compounds directed at the SKI complex as broadly acting antivirals.